It has become almost a cliché to say this but the last year and a half has been one of the calmest periods on Israel's borders, and in the statistics of casualty numbers quite possibly the calmest in its history.

Since the Gaza operation ended in January 2009, missiles from the Strip into Israel have lessened to a trickle, barely even a nuisance as almost all of them fall in uninhabited areas, quite often within Palestinian territory.

On the Lebanese border, quiet has reigned since the end of the Second Lebanese War exactly four years ago; in all this time seven Katyusha rockets have been fired, with the sole casualty one Israeli woman very lightly wounded by broken glass.

And in the West Bank, years of arrests, targeted assassinations and vigorous policing have eroded the terror organisations' capabilities to such a degree that they can launch nothing more that sporadic, primitive attacks.

The peace is now being enforced to a large degree through growing levels of co-operation with the Palestinian Authority's American-trained National Security battalions, who have a vested interest in maintaining the calm and reducing the power of its Hamas rivals. Israel's enemies are afraid of a devastating response, explain IDF generals. The war in Lebanon and Operation Cast Lead, despite their other, adverse, results, have re-established Israeli deterrence on the borders.

Three separate incidents over the space of five days - a rocket from Gaza hitting Ashkelon, without casualties; another missile from within Egypt, hitting Eilat and Aqaba, killing one Jordanian; and a surprise sniper attack on IDF soldiers on the Lebanese border, killing one and severely wounding another - may be just an unfortunate coincidence but they have raised the question of whether the deterrence is wearing thin.

While Hizbollah and Hamas have held fire, they have been rearming with Iranian help, and are better prepared now for the next round. Iran will undoubtedly try to influence that timing: could the events of last week be seen as a trial run?

While Iranian involvement can never be ruled out, it seems that in all three attacks, the causes are more localised. The attack on Ashkelon was carried out almost certainly by one of the smaller, jihadi movements in Gaza, and was an expression of their opposition to Hamas as much to Israel.

The missiles on Eilat and Aqaba were motivated also by internal Palestinian politics. With direct negotiations about to open between Israel and the PA, Hamas is looking for ways to remind everyone of its existence.

The Lebanese shooting is harder to decipher. Why did a low-level Lebanese Army officer give the order to open fire on an IDF command post? Was he acting on his own initiative or was this part of a wider attempt by the Lebanese Army and government to assert its own sovereignty?

While none of the parties may be interested right now in all-out war, it would hardly be the first case in which internal Palestinian or Lebanese rivalries spilled over into wider hostilities with Israel. With Iran busily mixing the pot, this is a strong possibility.